In the downhole drilling and completion arts, completion strings are configured with many varied construction strategies to promote many different types of properties. One type of completion string employs radially telescopic members that allow for a direct opening connection to the formation face from the inside dimension of the completion string. Such telescopic members are useful for operations such as focused fracing operations and for production directly through the members.
Telescopic members of the prior art have been deployed using mechanical means and pressure. Where pressure is the motive force behind moving the telescopic members radially outwardly, the opening in the members must be initially closed for pressure to build thereupon. Commonly the art has used burst disks since they can be configured to burst at a certain pressure and leave little residue. Unfortunately however, although it would appear that regulated pressure would facilitate positive and complete deployment of the telescopic units, in practice this is not always the case. Rather, due to unpredictable borehole conditions, some of the telescopic members may not fully deploy before the pressure gets to the threshold pressure of the burst disks. This will result in at least one of the disks rupturing. Because the system is pressurized all at once, a single disk bursting will be sufficient to lose all the pressure to the formation and hence have no residual pressure available for the further deployment of telescopic members not fully deployed before the first disk ruptures. With the popularity of telescopic members increasing due to the benefits they provide if fully deployed, the art will well receive new configurations promising greater reliability of deployment.